Fluidic Volume Dispense Verification Tool

ABSTRACT

Disclosed herein is a device for measuring fluid dispense volumes including one or more wells adapted to receive a fluid; a tube having an internal passageway fluidly coupled to the one or more wells, wherein fluid in the wells passes into the internal passageway via capillary action to form a fluid column having a meniscus spaced from the wells; and a scale coupled to the tube, the scale calibrated to provide an indication of the volume of the fluid based upon the location of the meniscus in the fluid passageway.

REFERENCE TO PRIORITY DOCUMENT

This application claims priority of co-pending U.S. Provisional PatentApplication Ser. No. 60/872,252 filed Dec. 1, 2006. Priority of theaforementioned filing date is hereby claimed and the disclosure of theProvisional patent application is hereby incorporated by reference inits entirety.

BACKGROUND

Disclosed herein are devices and methods for measuring reagent volumesand determining the accuracy of liquid dispensers used in biochemicaland biomedical assays. More particularly, disclosed herein are devicesused with robotic equipment in the processing of microtiter-plate basedassays. The devices and methods permit verification of the accuracy ofthe dispensing portion of diagnostic instruments in the analysis ofsamples.

The development of microtiter-plate methods allows the processing of alarge number of samples simultaneously. Several laboratory and roboticsystems have been developed for the purpose of processing microtiterplates. These devices are designed to increase laboratory throughput andare generally preferred over non-automated processes. Automated systemsare more efficient and easier to control with less chance for randomprocedural errors. Automated systems generate homogeneous assays andhave helped to eliminate error-prone washing and transferring steps.Automated systems generally provide for the accurate and precisedelivery of assay reagents and other necessary fluids to individualreaction vessels

Automation techniques vary from simple semi-automated liquid handlingsystems to fully integrated automated systems that include multiplerobot arms and pipetting stations. Although automated systems haveimproved quality and reproducibility of fluid transfer, periodiccalibration and quality assurance determinations are required. Therelatively small size of the wells on the microtiter plate requires theprecise delivery of a minute amount of sample. Inaccuracies in thedelivery of samples can lead to erroneous results. In order to safeguardthe accuracy of the results, the volume delivered by the automateddevices must be routinely verified. Assuring the accuracy of biochemicalassays is a critical concern for those in the medical diagnostic arts.

Two common techniques for checking the precision and accuracy of fluiddispensers are gravimetric and spectrophotometric techniques. Thegravimetric technique is based on the weight of a pure sample of waterdispensed by the device. The water is weighed using a balance calibratedwith NIST-traceable weights. The actual dispensed volume is calculatedfrom the measured weight and the density, taking into accounttemperature and evaporation rate. The proper type of equipment andoperating environment which are needed to make gravimetric verificationof automated pipetting devices are usually not available in a clinicallaboratory and requires a visit by a field service technician to performthe diagnostic tests on site. Precision balances are expensive anddifficult to use in the field service environment. They are sensitive tovarious environmental influences such as proximity to air conditioningvents, vibration and leveling. Precision balances also require carefulset-up and regular calibration to ensure proper function. Thus, theskill level and time required to conduct these measurements are veryhigh which makes gravimetric verification impractical in a clinicallaboratory.

The spectrophotometric technique of volume verification employs asolution containing a known concentration of a high-colored chromagen.Aliquots of the sample solution are dispensed into a known volume ofdiluent and the absorbance measured. The actual dispensed volume is thencalculated from the absorbance, the light path, the extinctioncoefficient and the diluent volume. In reality the concentration of thecolorimetric reagent, cannot be precisely controlled. Therefore,verification techniques that calculate volume directly from theabsorbance measured are often inaccurate. Furthermore, this method ofvolume verification is a manual procedure that is not performed incoordination with an automated workstation. The method requiresadditional solutions and is time consuming and prone to human error.

SUMMARY

Disclosed herein are devices and methods of use to verify the accuracyof fluid dispense volumes based upon capillary forces. The device andmethods are highly accurate, easy to use, portable and universallydesigned for use with automated dispensing workstations.

Disclosed herein is a device for measuring fluid dispense volumesincluding one or more wells adapted to receive a fluid; a tube having aninternal passageway fluidly coupled to the one or more wells, whereinfluid in the wells passes into the internal passageway via capillaryaction to form a fluid column having a meniscus spaced from the wells;and a scale coupled to the tube, the scale calibrated to provide anindication of the volume of the fluid based upon the location of themeniscus in the fluid passageway.

Other features and advantages should be apparent from the followingdescription of various embodiments, which illustrate, by way of example,the principles of the disclosed device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pictorial view of an exemplary volume dispenseverification device used in coordination with an automated workstationhaving a robotic arm.

FIG. 2A shows a perspective, transparent view of the volume dispenseverification device.

FIG. 2B shows a cross-sectional view of the device taken along lines B-Bof FIG. 2A.

FIG. 2C shows a cross-sectional view of the device taken along lines C-Cof FIG. 2A.

FIG. 3 shows an exploded view of the device of FIG. 2.

FIG. 4 shows a detailed view of the capillary block of the device ofFIG. 2.

FIG. 5 shows a conceptual diagram of the device of FIG. 2.

FIG. 6 shows an exemplary dynamic range of volumes determined by thedevice of FIG. 2.

FIG. 7 shows an exemplary percent coefficient of variance for the deviceof FIG. 2.

FIG. 8 shows exemplary volumes determined by the device of FIG. 2 usingmulti-dispensing techniques with an automated fluid handling instrument.

FIG. 9 shows exemplary percent coefficient of variant for each channelof the device of FIG. 2 using multi-dispensing techniques with anautomated fluid handling instrument.

DETAILED DESCRIPTION

Disclosed is a measuring device that is adapted to verify the accuracyof fluid dispense volumes based upon capillary forces. The deviceincludes a well that receives a volume of fluid. The well is fluidlycoupled to a capillary tube having a graduated scale. The fluid movesfrom the well into the capillary tube pursuant to capillary action. Asdescribed in detail below, the distance the fluid travels into thecapillary tube is used as a measure of the volume of the fluid that wasreceived into the well. The graduated scale on the capillary tube can becalibrated to provide an indication as to the volume of fluid that wasreceived into the well.

In an exemplary embodiment described herein, the device is used incombination with an automated workstation that transfers selectedvolumes of liquid (reagents, diluents and samples) to microtiter platewells for transfer of sample to and from microtiter plates. Pursuant tosuch use, the device is described herein as being sized and shaped tointeract with standard microtiter plates. However, it should beappreciated that the measuring device can be sized and shaped in othermanners and is not limited to the particular embodiment describedherein.

FIG. 1 shows an exemplary embodiment of a measuring device 105 in usewith an automated workstation 100. The automated workstation 100 can be,for example, the NanoChip® 400 System (NC400 Nanogen, Inc., San Diego,Calif.) The automated workstation 100 includes a robotic type instrument110 in which a robotic arm 115 transfers selected volumes of liquid(reagents, diluents and samples) to microtiter plate wells 120 fortransfer of sample to and from microtiter plates 125. Standardmicrotiter plate wells 120 are arranged in rows and columns, for examplean 8×12 assay of wells 120. The samples to be processed are held in asample carrier location, labeled “Position 1” and “Position 2” in thefigure. Dispensing pipette(s) 130 mounted on the robotic arm 115 canwithdraw samples from the sample locations and transfer them tomicrotiter plate wells 120 of microtiter plates 125. Additionalaccessories can be incorporated into the automated workstation such as acomputer 135 that runs software known in the art to control theautomated workstation 100. Reagent and diluent reservoirs can also beincorporated into the automated workstation 100. It should beappreciated that the use of the device 105 with the automatedworkstation 100 is exemplary and that the device 105 can be used inother settings and environments. In addition, the automated workstation100 is not limited to the particular configuration shown in FIG. 1.

The pictorial view of FIG. 1 shows the device 105 positioned within asample carrier shown as position 1 of the automated workstation 100. Inone embodiment, the device 105 is dimensioned to coincide with thedimensions of microtiter assay plates known in the art, for exampleNunc™ microtiter plates. This provides the device 105 with a universalconfiguration that allows for the device 105 to be used with a varietyof microtiter plate machines, including automated workstations,regardless of brand or type of machine. The device 105 can also bedimensioned according to other types and sizes of microtiter plates oraccording to other dimensions.

As shown in FIGS. 2A, 2B and 2C, in an exemplary embodiment the device105 generally includes a base 205, dispense block 210, dispense blockcover 280, cover 215, at least one capillary tube 220, at least 1 seal245, and at least one metering element 230. The capillary tubes 220 andmetering elements 230 are sandwiched between the base 205 on theunderneath surface and the cover 215 on the upper surface. The dispenseblock 210 has wells 240 that are each connected to a respectivecapillary tube 220, the tubes 220 extending longitudinally across thebase 205. The figures show the device having a plurality of capillarytubes coupled to a plurality of wells, although it should be appreciatedthat the device could include only a single capillary tube and a singlewell or a plurality of wells attached to a single capillary tube.

The base 205 can be inserted into standard sample carriers of knownmicrotiter plate devices, including automated workstations. As bestshown in FIGS. 2C and 3, in an exemplary embodiment the upper surface ofthe base 205 has at one end a rectangular, shallow recess 257 surroundedon three sides by a raised portion 255. The upper surface of the base205 also has evenly distributed longitudinal channels 250. The channels250 extend from the recess 257 on one end to a groove 260 at theopposite end of the base 205. The groove 260 lies perpendicular to thechannels 250. The base 205 acts as a support structure in that itsupports and provides a surface for the metering elements 230 andcapillary tubes 220 to be positioned. The structure shown in the figuresis merely exemplary and can be varied. For example, the recess 257 neednot be rectangular and the channels do not have to be evenlydistributed.

As shown in FIGS. 2A, 2C, 3 and 4, the exemplary embodiment of thedispense block 210 has one or more dispense wells 240 in its uppersurface. In one embodiment, the wells 240 are dimensioned and spacedaccording to wells of known standardized microtiter plates, for examplethe 8×12 or 96-well Nunc™ microtiter plates, although the wells 240 canbe dimensioned and spaced in other manners. When the dispense block 210is positioned in the recess 257 of the base 205, the wells 240 canreceive fluid, for example, from a pipette 130 of an automatedworkstation 100. In the exemplary embodiment, the column of wells 240 isarranged in the standardized configuration as wells of microtiter platesknown in the art, so that the device 105 is universal with any fluidhandling machine that accepts microtiter plates known in the art.However, the arrangement of the wells can be varied. The dispense wells240 have an intake 216 drilled at or near the bottom of the wells 240.

The dispense block 210 also has one or more openings or holes thatreceive the capillary tubes 220 such that the capillary tubes enter thedispense block 210 and couple to the intake 216 of the dispense wells240. Thus, the capillary tubes 220 and dispense wells 240 are in fluidcommunication with one another at intake 216. As best shown in FIG. 4,in the exemplary embodiment eight capillary tubes 220 connect to theirrespective dispense wells 240 at intake 216 at or near the bottom of thewell 240. In one embodiment, as shown in FIG. 5, the angle θ between thedispense wells 240 and the capillary tubes 220 near the region of theintake 216 can be about 90 degrees from vertical. In other embodiments,the angle θ between the dispense wells 240 and the capillary tubes 220near the region of the intake 216 can be about 85 degrees, about 80degrees, about 75 degrees, about 70 degrees, about 65 degrees, about 60degrees, about 55 degrees, about 50 degrees, about 45 degrees, orbetween about 0 degrees and about 90 degrees from vertical. The shape ofthe dispense wells can vary. In one embodiment, the dispense wells 240have hemispherical bottoms and can include v-shape, u-shape or otherround well bottoms. The round-shaped well bottom is conducive to thecomplete transfer of fluid inside the well 240 into the capillary tube220. Round bottom wells avoid residual fluid volume collecting insidethe well, which can occur, for example, with flat-bottomed wells.

With respect to FIGS. 2A and 2C, the dispense block 210 is positioned inthe recess 257 of the base 205. The upper surface of the dispense block210 can lie flush with the upper surface of the three walls of theraised portion 255. When the dispense block 210 is positioned in therecess 257, the capillary passages 214 align with the channels 250 ofthe base 205 and with channels 270 of the cover 215, as described inmore detail below. The longitudinal channels 250 and 270 provide asurface in which the portion of the capillary tubes 220 extending beyondthe dispense block 210 can reside. The majority of each capillary tube220 can reside within the channels 250 and 270 of the base 205 and cover215 and a smaller segment of each capillary tube 220 can reside insidethe dispense block 210.

As best shown in FIG. 4, the capillary passages 214 are surrounded byseal members 245, such as O-rings or the like. The capillary passages214 can be counter-bored such that the seal members 245 are positionedinside counter-bores within the wall 212 of the dispense block 210. Inone embodiment, the seal members 245 are slightly compressed by thedispense block cover 280 (best shown in FIG. 2C) such that compressionforces generate a seal around each capillary tube 220. The seal members245 increase the likelihood that all of the fluid from each well 240enters its respective capillary tube 220 and prevent leakage of fluidaround the capillary tube 220. The seal members 245 also greatly reducethe elasticity of the fluid slug within the capillary tube 220, whichcan make accurate readings difficult. Similarly, generation of airbubbles inside the capillary tubes 220 is reduced by the presence of theseal members 245.

With respect to FIGS. 2A, 2B, 2C and 3, the cover 215 sits on top of thedevice 105 such that one end of the cover 215 abuts the raised portion255 of the base 205 as well as the dispense block cover 280. Similarly,the upper surface of the cover 215 can lie flush with the upper surfacesof the raised portion 255, the dispense block cover 280 and dispenseblock 210. On its lower surface, the cover 215 has a series of channels270 that correspond to the channels 250 of the base 205. The channels270 extend longitudinally from the end of the cover 215 that abuts thedispense block cover 280 to the opposite end where there runs a groove275. The groove 275 corresponds to the groove 260 of the base 205 andcan lie perpendicular to the channels 270.

The base 205 and cover 215 are attached to each other by fixationelements 235, such as screws, bolts, etc. The base 205 and cover 215 canalso be attached by other fixation methods such as by using glue. In thecase of screws or bolts, apertures 237 can extend through the cover 215and apertures 239 can extend through the base 205. When the device 105is assembled, apertures 237 align with apertures 239. Fixation elements235 can be inserted through the aligned apertures 237, 239 fixing thecover 215 to the base 205. When the cover 215 and the base 205 are fixedto one another, they sandwich the capillary tubes 220 and meteringelements 230. As best shown in FIG. 2B, the base 205 and cover 215 thatsandwich the capillary tubes 220 can lie flush against one another byvirtue of their longitudinal channels 250, 270. The channels 250, 270correspond and align with one another forming longitudinal passagewaysthrough which the capillary tubes 220 can extend. As mentioned, theparticular structure of the device assembly is merely exemplary and itcan be varied.

As described above, the capillary tubes 220 and metering elements 230are sandwiched between the cover 215 and the base 205 (shown in FIGS.2A, 2B and 2C). The capillary tubes 220 reside within the longitudinalpassageways formed by the channels 250, 270. The metering elements 230are graduated scales that are used to measure the length of the fluidslug or the distance the fluid slug travels within the capillary tube220. The metering element 230 can be positioned next to each capillarytube 220 or can be positioned next to every other capillary tube 220such that a metering element 230 lies between a pair of capillary tubes220, as shown in the Figures. Alternatively, the entire base 205 can becovered by a metering element 230. The perpendicular grooves 260, 275that align at one end of the device 105 prevent the wicking of fluid bythe metering elements 230 from the end of the capillary tube 220 thatcould potentially occur.

In use, fluid is dispensed into one or more of the wells 240. The fluidpasses through the intake and into a respective capillary tube 220. FIG.5 shows a conceptual diagram of the device 105. The movement of thefluid from the well 240 into the capillary tube 220 is governed by thecapillary force equation. The height h of a liquid column is governedby:

$h = \frac{2\; T*\cos \; \theta}{pgr}$

-   -   where    -   T=surface tension (J/m² or N/m)    -   θ=contact angle    -   p=density of fluid (kg/m³)    -   g=acceleration due to gravity (m/s²)    -   r radius of tube (m)        Capillary movement occurs when the adhesive intermolecular        forces between the fluid and the tube 220 are stronger than the        cohesive intermolecular forces within the fluid. Surface tension        pulls a fluid column into the capillary tube 220 until there is        a sufficient weight of fluid for gravitational forces to        overcome the intermolecular forces. The weight of the fluid        column is proportional to the square of the tube's diameter, but        the contact area between the fluid and the tube is proportional        only to the diameter of the capillary tube 220. Thus, a narrow        tube will draw a fluid column further than a wide tube.        Capillary tubes 220 used in the disclosed device 105 can        include, for example, 90 μL capillary micropipets (#1-000-0900;        Drummond Scientific Co., Broomall, Pa.). Increasing the contact        angle causes the distance that the fluid travels in the        capillary tube 220 to decrease. Setting the contact angle to        horizontal or zero maximizes the distance that the fluid can        travel in the capillary tube 220.

In the disclosed system, there is also a pressure differential betweenthe fluid in the dispense well 240 and the air in the capillary tube 220that also contributes to the flow of fluid into the capillary tube 220.In the dispense well 240, the weight of the fluid near the top causespressure on the fluid near the bottom of the well 240 to increase. Theregion of higher pressure (P_(H)) near the bottom of the well 240 forcesthe fluid to flow toward the region of lower pressure (P_(L)) inside thecapillary tube 220. At some point, all forces acting to pull fluid Finto the capillary tube 220 equalizes and the flow stops. At this point,the meniscus M can be measured against a graduated scale or meteringelement 230 to determine how far the fluid moved. The distance the fluidtraveled in the capillary tube 220 is a direct measure of the volume ofthe fluid.

Prior to use of the device 105, calibration curves can be generated foreach channel of the device 105. This can be done by hand pipetting arange of fluid volumes into each well 240 of the device 105 andmeasuring the length of the fluid slugs against the metering elements230. By plotting the known volumes from the pipettor versus the numberof graduated lines from the metering element 230, a linear equation canbe developed for each channel of the device 105 in order to correlatethe graduations on the metering element 230 to volume.

To verify the accuracy and precision of volumes dispensed by, forexample, automated workstations, the user places the device 105 onto asample carrier of an automated workstation 100 and a dispenseverification test is run. The device 105 can be evacuated by blowingcanned air into the wells such that all residual moisture is removed.Service software can be used to run the test or the test can be runmanually. A volume of reagent is aspirated and dispensed, such as by aninstrument robot 110, into one or more of the dispense wells 240. Avariety of dispense methods can be used. For example, the single aliquotmethod can be used where one aliquot of fluid is aspirated and thendispensed into each well. Alternatively, a multiple dispense method canbe used where a larger volume of fluid is aspirated and then one aliquotdispensed into multiple wells. Fluid dispensed into the wells 240 istransferred from the well 240 into the capillary tube 220 by capillaryaction. The fluid travels some distance in the capillary tube 220 andthen stops. At this point, the user can read the position of themeniscus M of the fluid with respect to the metering elements 230.

The readings can be performed manually or by using automatedvisualization techniques known in the art. One or more parts of thedevice 105 can be made of transparent or translucent material to allowfor more accurate readings. Calibration curve generation can beperformed to correlate the measured distance traveled by the fluidwithin the capillary tube 220 of the device 105 to an actual volume offluid dispensed. Once a calibration curve is generated, the distancethat the fluid travels into the capillary tube (as measured relative tothe metering elements 230) is used as a measure of the volume of fluidthat was dispensed into the well. The conversion from the distancetraveled to volume can be performed manually using the calibration curveor it can be performed automatically using a computer into which thecalibration curve has been entered. In one embodiment, the calibrationis performed and the metering element 230 is configured such that itdisplays a scale of fluid volumes rather than distance of the fluid intothe capillary tube. Calibration curves can be generated for eachcapillary tube 220 such as described in Example 1.

Surface tension, viscosity, density and temperature of the fluid canlead to different dispensed volumes. For example, the addition of asolute (buffer, preservative, protein or chromagen) to the fluid canlower the surface tension and increase the dispensed volume. Therefore,a calibration curve can be created for each fluid type to be dispensed.Further, the configuration of the capillary tubes 220 with the dispensewells 240 can also be adjusted for fluids of varying surface tensions.For example, for fluids with slightly lower surface tension thecapillary tubes 220 can be inserted further into the dispense wells 240at intake 216 to restrict flow. For fluids with slightly higher surfacetension, the capillary tubes 220 can be pulled further away from theintake 216 to allow more flow.

The range of fluid volumes that can be verified using the discloseddevice 105 includes, for example, volumes between approximately 10 μland 100 μL, more specifically, volumes between approximately 20 μl and90 μl and even more specifically, volumes between approximately 25 μland 85 μl. Volumes can be verified to less than about 1 μL precision andto an accuracy of about ±1 μL between about 30 μL and 65 μL; ±3 μLbetween about 15 μL and 30 μL; +2/−1 μL between about 65 μL and 70 μL.

The following examples are included for illustrative purposes only andare not intended to limit the scope of the claims.

EXAMPLES Example 1 Calibration Curve Generation

Calibration curves are generated for individual capillary tubes of thedisclosed volume verification device. A 2% ethanol solution is pipettedinto each dispense well using fluid volumes ranging between 20 μL to 80μL. The number of marks on the graduated metering element to themeniscus of the fluid in the capillary tubes are counted, such as bymanual methods. Table 1 shows the number of marks to the meniscus foreach capillary tube (tubes 1-8) at each volume dispensed (20 μL, 30 μL,40 μL, 50 μL, 60 μL, 70 μL and 80 μL). The data are plotted and fit tolinear equations to convert distance the fluid moved in the capillarytubes to volume of fluid dispensed into the wells.

TABLE 1 Calibration curve data using 2% EtOH solution 20 30 40 50 60 7080 slope y-int 1 6 14.5 20.5 30.5 39 48.5 52 0.80 −9.95 2 6 13 21.5 3038.5 46 54 0.81 −10.68 3 5 14.5 23 31 38 45 56.5 0.82 −10.73 4 4 14.519.5 31 38 46 54 0.83 −11.77 5 7 13.5 21.5 30.5 39 49 54 0.82 −10.34 6 615.5 23.5 31.5 37 45 54.5 0.78 −8.50 7 6.5 14.5 22.5 30.5 36 45.5 530.77 −8.61 8 6 14 20.5 31.5 40.5 47 57.5 0.86 −11.95

Example 2 Comparison of Volume Verification Device to Gravimetric VolumeVerification Methods

Volumes measured using the disclosed volume verification device arecompared to gravimetric techniques. Fifty μL of 2% EtOH is pipetted intoeach of the 8 wells of the volume verification device using a GilsonRainin P200 Pipetman (Table 2) or an automated fluid handling instrumentNC400 (Table 4). The fluid volumes are measured using the calibrationcurves generated by the method described in Example 1. Subsequently, 50μL aliquots of 2% EtOH is dispensed using an automated fluid handlinginstrument (NC400, Nanogen, Inc.) onto a Mettler Toledo PB3002 Balanceand a Mettler Toledo AT200 Balance (Table 3). The results indicated thatthe disclosed volume verification device measures to a precision of 0.5L whereas the Mettler Toledo AT200 precision balance measures to aprecision of 0.1 μmg or 0.1 μL. The Mettler Toledo PB3002 balance is notadequate to measure at this volume.

Comparing the coefficient of variance (% cv) when volumes are dispensedusing the automated fluid handling instrument shows nearly equivalentresults between the AT200 balance and the disclosed device. The AT200%cv is 1.89% while the average of all channels on the disclosed device is2.00%. The % cv measured when the device is loaded manually with thepipettor is found to average 3.97%. This indicates that a manualpipettor is less precise than the automated NC400 syringe pump androbot. This data also indicates that the error measured in the discloseddevice and the AT200 balance are nearly the same and that the bulk ofthe error is most probably due to the NC400 syringe pump and robot.

TABLE 2 Volumes read on device when loaded by hand using Gilson P200Pipetman Channel 1 2 3 4 5 avg sd % cv range 1 48.6 49.8 51.1 52.3 51.750.69 1.50 2.96% 3.7 2 50.2 50.2 50.2 49.6 50.8 50.18 0.44 0.87% 1.2 352.5 51.9 51.3 48.3 49.5 50.69 1.77 3.49% 4.3 4 51.1 52.9 52.3 50.5 50.551.49 1.10 2.13% 2.4 5 52.9 49.2 49.2 49.2 47.4 49.58 2.00 4.04% 5.5 653.3 48.8 52.7 50.1 50.7 51.12 1.85 3.62% 4.5 7 53.5 51.6 50.3 49.0 50.350.93 1.72 3.38% 4.6 8 50.6 51.7 51.7 47.7 51.2 50.58 1.70 3.36% 4.1

TABLE 3 Volumes read on Mettler Toledo balances when dispensed withNC400 Instrument 0110 Mettler Toledo PB3002 (QA486) Mettler Toledo AT200(QA075) Calibrated October 2006 Calibrated February 2006 Tube Pre (g)Post (g) diff uL Tube Pre (mg) Post (mg) diff uL 1 0.9 0.94 0.04 40 1897.7 945.3 47.6 47.6 2 0.91 0.95 0.04 40 2 903.7 952.5 48.8 48.8 3 0.890.94 0.05 50 3 881.6 928.9 47.3 47.3 4 0.9 0.95 0.05 50 4 896 943 47 475 0.9 0.94 0.04 40 5 913.5 962.8 49.3 49.3 6 0.9 0.95 0.05 50 6 891.5938.5 47 47 7 0.91 0.95 0.04 40 7 891.1 940.4 49.3 49.3 8 0.89 0.94 0.0550 8 888.6 937.1 48.5 48.5 9 0.88 0.93 0.05 50 9 892.1 939.4 47.3 47.310 0.88 0.93 0.05 50 10 899.6 947.5 47.9 47.9 avg 46 avg 48 sd 5.163978sd 0.907989 % cv 11.23% % cv 1.89% range 10 range 2.3

TABLE 4 Volumes read on device when dispensed with NC400 Instrument 0110Oct. 20, 2006 Instrument delivered fluid (50 uL, H2O, Converted to uLusing calibration curves) Channel 1 2 3 4 5 6 7 8 9 10 avg sd % cv range1 48.6 49.8 49.2 49.2 49.2 49.2 49.2 49.2 49.2 49.2 49.20 0.29 0.60% 1.22 49.6 49.6 49.6 49.6 49.6 49.6 49.6 51.4 50.8 49.6 49.87 0.67 1.34% 1.93 48.9 48.9 49.5 49.5 50.7 48.9 48.9 50.1 49.5 49.5 49.42 0.60 1.22% 1.84 52.3 50.5 50.5 52.9 52.9 50.5 52.3 50.5 50.5 52.9 51.61 1.17 2.26% 2.45 48.6 49.2 51.7 49.2 51.7 51.7 51.0 49.2 49.2 51.7 50.32 1.31 2.61% 3.16 52.0 52.7 52.7 50.1 52.0 52.7 50.1 50.1 52.7 50.1 51.50 1.24 2.41% 2.67 51.6 51.6 49.0 49.0 52.9 52.2 49.6 52.9 49.6 51.6 50.99 1.55 3.04% 3.98 50.6 49.4 48.8 48.3 48.8 51.7 48.3 48.8 47.7 48.3 49.07 1.23 2.51% 4.1

Example 3 Determination of the Dynamic Range of the Volume DispenseVerification Device

To determine the dynamic range of the disclosed device, varying dispensevolumes of either deionized water (DI H₂O) or 2% ethanol (ETOH) solutionare loaded into each of the eight wells using the NC400 automated fluidhandling instrument. FIG. 6 shows the volumes determined by the deviceas having an optimum usable range between 20 μL to 85 μL. At smallervolumes, fluid can stick to the walls of the dispense well and are notdrawn into the capillary tube. Lightly tapping the device shifts thefluid into contact with the capillary tube such that the fluid will flowinto the device.

FIG. 7 shows the percent coefficient of variance (% cv) for each channelof the device. The data indicate that the % cv could have been improvedfor channels 5-8 lowering the flow rate, such as by pushing thecapillary tubes inward slightly.

Example 4 Volume Verification Using Multi-Dispensing Techniques

One large volume is aspirated by a robotic pipette on an automated NC400device and equal sized smaller aliquots are dispensed into the eightwells of the device (FIG. 8). FIG. 8 shows that the robotic pipetteaspirated volumes of 160 μL, 240 μL, 320 μL, or 400 μL and dispensedinto each of the eight channels aliquots of 20 μL, 30 μL, 40 μL, or 50μL, respectively. Thus, fluid volume aspirated is equal to the dispensevolume divided by eight. FIG. 8 shows that the final well dispensed(well 8) frequently measured a smaller volume than the target dispensevolume. Thus, to insure a more accurate and consistent volume dispensefor each well, the starting aspirated fluid volume should be slightlygreater than the cumulative volume of the eight dispensed volumes.

FIG. 9 shows that multi-dispensing lowers the % cvs which averages 1.19%and that the expected linear relationship of % cv decreases as volumeincreases. The data also provides further evidence that precision andaccuracy of the device is equivalent to gravimetric methods using aprecision balance (i.e. as low as 0.1 mg). When comparing singledispense to single dispense the % cvs are equivalent. Further, removingair gaps in the dispense system lowers % cvs.

Although embodiments of various devices are described herein in detailwith reference to certain versions, it should be appreciated that otherversions, embodiments, methods of use, and combinations thereof are alsopossible. Therefore the spirit and scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

1. A device for measuring fluid dispense volumes, comprising: one ormore wells adapted to receive a fluid; a tube having an internalpassageway fluidly coupled to the one or more wells, wherein fluid inthe wells passes into the internal passageway via capillary action toform a fluid column having a meniscus spaced from the wells; and a scalecoupled to the tube, the scale calibrated to provide an indication ofthe volume of the fluid based upon the location of the meniscus in thefluid passageway.
 2. The device of claim 1, further comprising a supportstructure, wherein the support structure supports the tube having aninternal passageway fluidly coupled to the one or more wells.
 3. Thedevice of claim 2, wherein the support structure can be removablyreceived and secured in a sample carrier of a liquid handling system. 4.The device of claim 3, wherein the sample carrier is adapted to receivea standardized microtiter plate.
 5. The device of claim 1, wherein theone or more wells are fluidly coupled to a dispensing passageway of aliquid handling system.
 6. The device of claim 1, wherein the one ormore wells are spaced according to the spacing of a standardizedmicrotiter plate.
 7. The device of claim 1, wherein at least one of theone or more wells has at least a partial spherical-shape.
 8. The deviceof claim 1, wherein at least one of the one or more wells has a roundedshape.
 9. The device of claim 1, wherein at least one of the one or morewells has a V-shape.
 10. The device of claim 1, wherein the couplingbetween the tube and the one or more wells forms an angle of at leastabout 90 degrees from vertical.
 11. The device of claim 1, wherein thecoupling between the tube and the one or more wells forms an angle of atleast about 85 degrees from vertical.
 12. The device of claim 1, whereinthe coupling between the tube and the one or more wells forms an angleof at least about 80 degrees from vertical.
 13. The device of claim 1,wherein the coupling between the tube and the one or more wells forms anangle of between about 0 degrees and about 90 degrees from vertical. 14.The device of claim 1, further comprising a support structure thatsupports the tube and further comprising a seal member that provides aseal between the tube and the support structure.
 15. The device of claim14, wherein the seal member is an o-ring.